Autism rates rose again. Experts explain why

Autism is more common than ever before, a new report suggests.

As of 2022, about 1 in 31 children in the United States were diagnosed with autism by the time they were 8 years old, researchers reported online April 15 in the Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report. Previous studies had put the number at 1 in 36 in 2020 and 1 in 150 in 2000. 

Many researchers view the report as a better reflection of the true rate of autism and an opportunity to help individuals and families in need.

“The thing I think that everyone can state, without question or controversy, is that the work really does highlight how unbelievably common autism now is across communities in the U.S.,” says Zachary Warren, a clinical psychologist at Vanderbilt University Medical Center in Nashville and a coauthor of the study. “I think we should be doubling our commitment towards finding answers and for building better services.”

To some people, though, this increase is shocking. That includes Robert F. Kennedy, Jr., the Secretary of the U.S. Department of Health and Human Services, who gave a dire view of the numbers in an April 16 news briefing. To Kennedy , those increases signal an “epidemic” of a disorder that “tears families apart.” 

That perspective has been denounced as a harmful characterization of autism. “Treating us like a disease or a burden on society, instead of living people who exist and have our own thoughts and ideas about our disabilities, weaponizes pity and fear to deny our basic rights,” the Autistic Self Advocacy Network responded in a statement.

Autism is an incredibly complex condition that has proven challenging to figure out. But over decades of research, scientists have made a lot of progress in understanding the risk factors for autism and how best to identify and help people who need support. Science News talked with five autism experts about what we know — and still don’t know — about the condition. 

What is autism?

Autism is a continuum of neurological differences collectively known as autism spectrum disorders (ASD). At the severe end, people may be nonverbal or have intellectual disabilities, behavioral problems or medical conditions that require intensive treatment. Toward the other end of the spectrum, people may think a little differently than others, or have light or sound sensitivities, for instance, but require fewer if any accommodations. 

Some people with autism embrace the condition as part of their identity, not a disorder that needs to be prevented or cured. 

“There’s no one true presentation of autism,” Warren says. “Autism, fundamentally … is a word that we use as our best attempt to describe and understand these uniquely wonderful kids that have strengths, but also some tremendous areas of vulnerability and impairment.”

How many people have autism? 

The exact number of people with autism isn’t known. The new report measured the prevalence of autism in 16 places in the United States among 8-year-olds. The study suggests an overall autism prevalence of 32.2 for every 1,000 kids, with variation across the states. 

Multiracial, Black, Hispanic, American Indian or Alaska Natives and Asian and Pacific Islander children had higher rates of autism than did white children, a reversal of results from earlier studies. Boys are still more likely to be diagnosed with autism than girls, the report says, but autism rates are increasing among girls.

Why are the numbers of children diagnosed with autism increasing? 

Kennedy claimed — against scientific evidence — that toxins are responsible, and he has vowed to find the culprit or culprits within months. He disputed the idea that these “relentless increases are simply artifacts of better diagnoses, better recognition or changing diagnostic criteria.” 

Yet that view contrasts sharply with many expert opinions and study conclusions, including the new report itself. Improved awareness and detection of autism account for much of the increase, according to many scientists. “The vast majority of this, I really think, is just recognition or better detection and diagnosis,” says pediatrician Dennis Kuo of the University of Rochester Medical Center in New York and former chair of the American Academy of Pediatrics’ Council on Children with Disabilities. “We just know a lot more about what to look for.”

Among children aged 8 years in 2022, ASD prevalence was 32.2 per 1,000 children (one in 31) across 16 sites, ranging from 9.7 per 1,000 in Texas to 53.1 per 1,000 in California.

And in a lot of ways, that’s a good thing, Kuo says. “I really see the rise in prevalence as a sign of progress,” he says. “It’s not so much about the diagnosis. It’s about the recognition of the needs and supports. And the earlier we are able to address these needs and supports … the better.” 

States had big differences in their autism rates, the new report showed. The prevalence of autism varied from 9.7 of every 1,000 kids in Laredo, Texas, to 53.1 of every 1,000 in California. However, “research has not demonstrated that living in certain communities puts children at greater risk for developing ASD,” the researchers wrote in their report. Instead, this discrepancy gives credence to the idea that better monitoring and screening is behind the increase. 

“In California, they have a really well-developed system where they do screening and linking children to services,” says Maureen Durkin, an epidemiologist at the University of Wisconsin-Madison. 

And researchers are increasingly realizing that autism may occur alongside other conditions, Warren says. “Individuals that might have received a diagnosis of a clinical disability [in the past], or been labeled with a number of different behavioral, psychiatric or learning issues, are now more likely to get diagnosed with autism as well.” 

Other factors could contribute to the increase. Preterm birth, for instance, is a risk factor for autism, and over the years, more babies born early have been surviving, Durkin says. “That could be contributing both as a cause of autism, and a cause of the rise,” she says. “But it can’t explain the entire rise.” 

Research also shows that older fathers are more likely to have children with autism because of a slight uptick in mutation rates with age, and that the age of fathers has risen slightly in recent years. “Older parents could be a small contributor, just like having children later contributes to Down syndrome,” says Daniel Geschwind, a neurologist and geneticist at the UCLA David Geffen School of Medicine. “But that’s not really enough, if you calculate it out, to account for the massive increase.”

Is autism genetic?

Yes, in part. But that yes comes with a lot of caveats. “There isn’t one cause for autism, and there isn’t one autism,” Landa says. “Autism isn’t one thing, just like dementia is not one thing. Cancer is not one thing.” 

Autism is what’s known as a neurodevelopmental disorder, which means that the way the brain grows and develops, beginning in pregnancy, is different in people who will go on to have autism. Genes play a role in that process. 

Geneticists have found that autism “is among the most heritable of neuropsychiatric disorders,” Geschwind says. Scientists have uncovered autism-related variations and mutations in about 200 genes, especially ones involved in early brain development. Most of those genetic signatures are inherited from a person’s parents, accounting for about 80 percent of autism cases, he says.  Another 10 to 15 percent of autism cases arise from new, or de novo, mutations in the child. 

“Virtually 95 percent of autism really can be accounted for by inherited factors or de novo and recessive mutation. So there isn’t a lot of other room for other things,” Geschwind says. 

Except in a few cases, though, genes alone don’t account for all of the risk of autism. People may have different combinations of genes that could put them at higher risk. But it might take something extra to alter brain development, Geschwind says. “There’s [a] certain amount of genetic risk that can be absorbed without having autism, and then past that point, you pass that liability threshold” and develop the condition.

What else could influence a person’s risk of autism? 

Countless factors can influence early brain development and therefore, affect the chance that a baby will later have autism. A complex interplay of experiences and exposures in the womb might alter brain development in people with genetic vulnerability, pushing them toward autism.

“Everyone wants it to be simple,” Warren says. “But the answers are supercomplex, and in part, they’re supercomplex because autism itself is supercomplex.”

Infections during pregnancy, such as with rubella or cytomegalovirus, known as CMV, have been linked to autism. So has the use of some epilepsy drugs, including valproic acid, early in pregnancy. Researchers have been investigating a host of other possibilities, including prenatal exposure to maternal obesity, medicines, air pollution, asthma triggers and cigarettes. The list of possibilities is long.

Some guesses, though, have been ruled out, including emotionally distant parenting, prenatal exposure to antidepressants, ultrasounds and, perhaps most thoroughly, vaccines. Many studies involving thousands of children around the world have amassed evidence that vaccines do not cause autism. 

Can you prevent autism?

In many ways, no. And many people in the autism community find talking about prevention offensive, Landa says, because it implies that people with autism are not worthwhile, valuable human beings. “Where we want to think about prevention is preventing these severe manifestations that are very life-interfering for autistic people.”

For Kuo’s part, a focus on prevention is “a distraction from what we really need to be doing, which is supporting people with autism. There is so much evidence and experience that shows the progress we make when children are embraced and thrive in their homes and their communities.” 

Landa echoes that idea. “The biggest thing is for people to be able to live their life fully, and for them to have a high quality of life. These are important priorities.” Over the years, “we’ve made a lot of discoveries that have improved the quality of life of autistic people,” she says. “And yes, we have a long way to go, but I just want to say we’ve come a long way, too.”